8

I'm starting a bit of a collection of batteries which have been ejected during a crash and ended up with a destroyed balance lead. Is there anything other than disposing of them that I can do, assuming the cells are still in good condition?

5

If you're up for it, the fix you're looking for is to repair the connector with a new housing and new crimps (if the current ones are broken). Joshua Bardwell has an excellent YouTube video documenting how to do this, but I'll summarize here.

Most LiPo balance leads are terminated with the JST-XH connector:

enter image description here (cit.)

In the above picture, the balance lead is configured such that the left-most pin is ground/GND and then are in ascending order of voltage from left to right when the flat surface of the connector housing is facing upwards. For example, a correctly made 4s LiPo balance plug would be wired up like so from left to right:

  • GND
  • Cell 1 (4.2 V when fully charged)
  • Cell 2 (8.4 V when fully charged)
  • Cell 3 (12.6 V when fully charged)
  • Cell 4 (16.8 V when fully charged)

Repair instructions:

  1. Purchase a JST-XH connector kit like this one on Amazon and a JST-XH crimper tool like the Engineers PA-09 on Amazon if you know or anticipate you'll need to replace the crimped pins (there are cheaper crimpers available, but I've had little trouble crimping JST-XH with this one and it's a nice-feeling tool)
  2. Pick out a new connector housing that's the same size as the broken one
  3. Remove the lowest voltage pin (left-most pin in the above picture) from the broken housing using a pointy tool to lightly press down on the edge of the silver retention tab
  4. If the pin is broken/bent/deformed, cut/pull off the JST-XH crimp and re-crimp a new one on
  5. Insert the pin into the new housing with the little retention tab facing upward until the retention tab on the pin clicks into place
  6. Repeat steps 3-5 for each other pin in order of ascending voltage

I'd recommend only having one pin free of either connector housing for as much of the process as possible to avoid inserting them in the wrong order or accidentally letting two of the pins tough each other, which would short the cells together (be bad).

Afterward, you should check your work by using a multimeter to confirm that the voltages between GND and each pin are in ascending order from left to right.

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  • How difficult is this to do if instead of the just connector being damaged, the wire has been pulled from the cell itself? I have at least one battery where the connector there is no remaining wire coming out of the plastic wrapping the cells. – Carbon Soar Jun 13 at 22:06
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    Well, that's a bit of a separate question... a good one to ask! Repairing that is riskier because you'll need to open up the insulation around the battery pack and solder to the cell. It's definitely feasible, just more dangerous. – ifconfig Jun 13 at 22:41

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